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Homework Help: Multi-pulley and force problem

  1. Apr 11, 2010 #1
    1. The problem statement, all variables and given/known data
    http://i829.photobucket.com/albums/zz220/narfarnst/problem.jpg

    Find T1 through T5 and the force on the right side of the diagram above.
    (The force balances the weight, so the system is stationary).
    EDIT: Oh, and the pulleys and ropes are massless and there is no friction.

    2. Relevant equations
    F=ma, various rearrangements of T=m(g+/-a)


    3. The attempt at a solution
    Based on mostly intuition I've concluded that T1=mg (very sure about that one).
    I also think that T2 and T3 equally share the weight, so T2=T3=1/2mg.
    T4 has to equal mg+F for it to keep the system up
    And I'm not sure about T5 but I'm thinking that it equals mg because the system isn't accelerating.
    But I'm not at all 100% sure an these.

    Thanks!
     
  2. jcsd
  3. Apr 11, 2010 #2

    rl.bhat

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    Homework Helper

    The single rope has three segments. Each segments must have the same tension. That is the basic constrain in the pulleys.
     
  4. Apr 11, 2010 #3
    Intuition is fine, if you can then find a reason why it is so. Gravity and
    the tension of the rope are the only forces on the block, so they
    must be equal and opposite.

    Because the pulleys have no friction and no mass, there must be the
    same tension in the ropes on both sides. (if there were not they would
    start to accelerate infinitely fast)
    Ok
    but then the forces on the top pulley would be unbalanced
     
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